Microsoft tag name page duplicate entries

[StarGeek]

Several Xtra tags have duplicate entries.  One writable, the other not writable.
AlbumArtist
AlbumTitle
Category
EncodedBy
Genre
InitialKey
Mood
ParentalRating
Period
Publisher
Subtitle

These tags have plural named entries though I'm not sure if this is an error or not, as the singular is listed as writable, but the plural is not.
Composer
Composers
Conductor
Conductors
Director
Directors
Producer
Producers
Writer
Writers

Finally, DateAcquired is listed as vt_filetime but I can't seem to find a definition of what vt_filetime is.

[Phil Harvey]

Yeah, the Microsoft tags are a bit of a mess.  There seem to be 2 standards that Microsoft is using, neither documented very well.  ExifTool writes only one version of these tags.  I don't recall why some of the non-writable tag names are plural, but I'll look into this.

The vt_filetime is a Microsoft name for the date/time format they use.  It's a 64-bit integer of (going by memory here so don't quote me) 100 ns intervals since 1900, or something like that.

- Phil

Edit: The epoch for vt_filetime is actually 1601, not 1900, but this is the same for the simple 'date' format.  The difference is that this is stored inside a VT_VARIANT, instead of using a standard date/time format code.  I don't know why this is, but I needed to use a different format type to be able to write it the way Microsoft does.